My 97 5.0 explorer runs really rough (it has 219,171 miles on it), but it's not showing a check engine light (it does work), when idling, it goes up and down in rpms slightly, but it doesn't die. I do need to replace the engine mounts, and I suppose a tune up could solve the issue, but I don't make much money at all, as I'm working as a busser at a restaurant on the weekends. Could there be a simpler issue and/or fix?